Spread-spectrum communication unit

ABSTRACT

A set of spread-spectrum units is capable of operating as a base station or as a remote unit. Each spread-spectrum unit includes a base subunit or a remote subunit, each subunit having a receiver for receiving spread-spectrum signals at a first frequency transmitted from the spread-spectrum units; a signal despreader for despreading the spread-spectrum; a demodulator for demodulating the despread-spread-spectrum signals; a combiner for combining the demodulated signals, and a local signal; a converter for converting the combined signal to a base-data signal; a spread-spectrum circuit for processing the base-data signal; and a transmitter for transmitting at a second frequency the processed base-data signal as a base-spread-spectrum signal.

This application is a continuation of U.S. patent application Ser. No.12/497,973, filed on Jul. 6, 2009, which is a continuation of U.S.patent application Ser. No. 11/429,386 filed on May 5, 2006, whichissued as U.S. Pat. No. 7,564,808 on Jul. 21, 2009, which is acontinuation of U.S. patent application Ser. No. 09/994,290, filed onNov. 26, 2001, which issued as U.S. Pat. No. 7,054,278 on May 30, 2006,which is a continuation of U.S. patent application Ser. No. 09/878,647,filed on Jun. 11, 2001, which issued as U.S. Pat. No. 6,356,534 on Mar.12, 2002, which is a continuation of U.S. patent application Ser. No.09/133,047, filed on Aug. 13, 1998, which issued as U.S. Pat. No.6,295,288 on Sep. 25, 2001, which is a continuation of U.S. patentapplication Ser. No. 08/814,809, filed on Mar. 10, 1997, which issued asU.S. Pat. No. 5,926,465 on Jul. 20, 1999, which is a continuation ofU.S. patent application Ser. No. 08/268,186, filed on Jun. 29, 1994,which issued as U.S. Pat. No. 5,610,906 on Mar. 11, 1997.

BACKGROUND

This invention relates to spread-spectrum communications, and moreparticularly, to a method and system for handing off a base stationamong a plurality of users in a spread-spectrum network.

Spread-spectrum modulation is a well developed art, in terms ofgenerating chipping sequences, and spread-spectrum processing datasignals with the chipping sequences. Using this technology,communication links may be established among a transmitter and areceiver in remote locations. Also, networks may be established, using aconference calling spread-spectrum technique. Conference callingspread-spectrum techniques are disclosed in U.S. Pat. No. 5,179,572entitled SPREAD SPECTRUM CONFERENCE CALLING SYSTEM AND METHOD, toSchilling, and in U.S. Pat. No. 5,263,045, entitled SPREAD SPECTRUMCONFERENCE CALL SYSTEM AND METHOD, to Schilling.

A problem may exist where a spread-spectrum conference calling system isset up, but the base station may need to change hands. For example, in amilitary environment, a platoon may use spread-spectrum modulation forconference calling among the members of the platoon. A particular unitin the platoon may be designated as the base station. The cited priorart does not teach how to change a base station from one platoon toanother or what would happen among units in the platoon in the event itbecame necessary to effectuate such a change.

SUMMARY

A communication unit comprises a command signal generator for generatinga command signal. A transmitter transmits communication signals at oneof two frequencies and for transmitting the command signal. A receiverreceives communication signals at one of the two frequencies and forreceiving the command signal. Upon initiation of the command signal, thecommand signal is transmitted for receipt by all active units in thesystem and the unit transmitting the command signal receivescommunication signals at a selected frequency of the two frequencies andtransmits communication signals at another frequency. Upon reception ofthe command signal from another unit in the system, the unit receivingthe command signal transmits a communication signal at the selectedfrequency of the two frequencies and receives communication signals atthe another frequency.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate preferred embodiments of theinvention and together with the description serve to explain theprinciples of the invention.

FIG. 1A is a block diagram of a base subunit using a plurality ofmixers;

FIG. 1B is a block diagram of a base subunit using a plurality ofmatched filters;

FIG. 2A is a block diagram of a remote subunit using a mixer;

FIG. 2B is a block diagram of a remote subunit using a matched filter;and

FIG. 3 is a block diagram of a command subunit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference now is made in detail to the present preferred embodiments ofthe invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals indicate like elementsthroughout the several views.

The present invention provides a unique solution to the problem of aplurality of spread spectrum units in use in a mobile environment inwhich any one of the spread-spectrum units is vulnerable toneutralization while maintaining communication between all thespread-spectrum units remains crucial. The spread-spectrum changeablebase station finds application in a platoon of units, in an armyenvironment, or in a law enforcement application, where a transportablebase station might be set up for controlling a plurality of spreadspectrum remote units. The problem being addressed for each of theseapplications is what happens when the base unit becomes disabled ornonfunctional. In the military environment, the base station may bedestroyed. In a law enforcement situation, the mobility of the pluralityof spread-spectrum units may have a requirement that the base stationchange from one unit to another.

The spread-spectrum system has a plurality of spread-spectrum units,with each spread-spectrum unit having a base subunit, a remote subunit,and a command subunit. The use of the term “subunits” for designatingthe base subunit, remote subunit, and command subunit, is for purposesof illustrating the invention. The invention may be built as one totallyintegrated unit, or as a mixture of more than one unit.

The base subunit is illustratively shown in FIGS. 1A and 1B. The basesubunit includes receiving means, despreading means, demodulating means,combining means, converting means, spread-spectrum processing means, andtransmitting means. The despreading means is coupled between thereceiving means and the demodulating means. The combining means iscoupled to the demodulating means and the converting means. Thespread-spectrum processing means is coupled to the converting means andthe transmitting means.

The receiving means is shown in FIG. 1A as antenna 11 coupled to radiofrequency/intermediate frequency (RF/IF) amplifier and filter section12. The despreading means is illustrated as a plurality of mixers 13,14, 15. As shown in FIG. 1B, the despreading means may also be embodiedas a plurality of matched filters 22, 23, 24. Each of the plurality ofmixers 13, 14, 15 has a chipping-sequence g₁ (t), g₂ (t), . . . , g_(N)(t), respectively, for mixing with the received spread-spectrum signal.The plurality of chipping sequences is matched to the chipping sequenceof the desired spread-spectrum signal to be despread.

The demodulating means and combining means is shown as the demodulator16 and combiners 17A, 17B. Combiners 17A, 17B may be a single combinerperforming the combining function, or separate combiners. The convertingmeans is shown as an analog-to-digital converter 18. The spread-spectrumprocessing means is illustrated as product device 19, having a chippingsequence for spreading the data signal from analog-to-digital converter18. The transmitting means is illustrated as transmitter 20 and antenna21.

The RF/IF amplifier and filter circuits 12 are coupled to the antenna 11and to the plurality of mixers 13, 14, 15. The plurality of mixers 13,14, 15 is coupled to the demodulator 16 and combiner 17A, 17B. Theanalog-to-digital converter 18 is coupled to the combiner 17B and to theproduct device 19. The transmitter 20 is coupled to the product device19 and to antenna 21. Antenna 21 and antenna 11 may be the same antennawith the appropriate isolation circuits, or different antennas. TheRF/IF amplifier and filter circuits 12 receive at a first frequency, f₁,a plurality of spread-spectrum signals transmitted from the plurality ofspread-spectrum units. The plurality of spread-spectrum signals aredespread by the plurality of mixers 13, 14, 15. As shown in FIG. 1B, thedespreading means may also be embodied as a plurality of matched filters22, 23, 24. The output of the plurality of mixers 13, 14, 15 is aplurality of despread-spread-spectrum signals. The demodulator 16demodulates the plurality of despread-spread-spectrum signals togenerate a plurality of demodulated signals. The combiner 17A combinesthe plurality of demodulated signals. The combined plurality ofdemodulated signals and a local signal from the base station may becombined by second combiner 17B to generate a combined signal. The term“combined signal”, as used herein, is an analog signal including thevoice of the base station and the combined demodulated signals of thecombiners 17A, 17B.

The combined signal is converted to a base-data signal byanalog-to-digital converter 18. The term “base-data signal,” as usedherein, is the digital signal coming from the analog-to-digitalconverter 18, and includes the converted analog signals and the datasignal at the base station.

The product device 19 spread-spectrum processes the base-data signalfrom analog-to-digital converter 18, with a base-chipping sequence. Thespread-spectrum-processed-base-data signal is transmitted as abase-spread-spectrum signal by transmitter 20 at the second frequencyf₂. Antenna 11 and antenna 21 may be a single antenna, serving both thereceiver and transmitter.

The remote subunit is illustrated in FIGS. 2A and 2B and includes areceiver portion, a transmitter portion, receiving means, despreadingmeans, and demodulating means. The transmitting portion includesconverting means, spread-spectrum processing means and transmittingmeans. The receiving means receives at the second frequency thebase-spread-spectrum signal. The despreading means despreads thebase-spread-spectrum signal as a despread-base-spread-spectrum signal.The demodulating means demodulates the despread-base-spread-spectrumsignal as a base-analog signal.

The converting means converts a remote-analog signal to a remote-datasignal. The remote-analog signal typically is the voice of the remotestation. The base-analog signal typically is the plurality of voicesignals from the base station. The spread-spectrum processing meansprocesses the remote-data signal with a remote-chipping sequence. Thetransmitting means transmits at the first frequency thespread-spectrum-processed-remote-data signal as one of the plurality ofspread-spectrum signals, which are received at the base subunit.

As shown in FIG. 2A, the receiving means includes an antenna 31 andRF/IF amplifier and filter circuitry 32. The despreading means anddemodulating means are embodied as mixer 33 and demodulator 34,respectively. As shown in FIG. 2B, the despreading means may also beembodied as a matched filter 39. The RF/IF amplifier and circuitry 32 iscoupled between antenna 31 and the mixer 33. The demodulator 34 iscoupled to the mixer 33.

The base-spread-spectrum signal at antenna 31 is amplified and filteredby RF/IF. The base-spread-spectrum signal is despread by thebase-chipping sequence by mixer 33 to generate thedespread-base-spread-spectrum signal. The demodulator 34 demodulates thedespread-base-spread-spectrum signal as a base-analog signal. The outputof the demodulator 34 is the plurality of voice signals from the basestation.

The transmitter section of the remote subunit may have the convertingmeans embodied as analog-to-digital converter 35, the spread-spectrumprocessing means embodied as product device 36 and the transmittingmeans embodied as transmitter 37 coupled to antenna 38. The productdevice 36 is coupled between the analog-to-digital converter 35 and thetransmitter 37.

The analog-to-digital converter 35 converts the voice of the remotesignal, designated here as the remote-analog signal, to a remote-datasignal. The remote-data signal is spread-spectrum processed by theproduct device 36 using remote-chipping sequence. The output of theproduct device 36 is the spread-spectrum-processed-remote-data signal.The transmitter 37 transmits the spread-spectrum-processed-remote-datasignal using antenna 38, as one of the plurality of spread-spectrumsignals. Antenna 31 and antenna 38 may be combined as a single antennaserving both functions.

The command subunit is illustrated in FIG. 3. The command subunitincludes initiating means, broadcasting means, and receiving means. Theinitiating means initiates a command signal, upon activation by thelocal user of that spread-spectrum unit. The command signal activatesthe base subunit in that spread-spectrum unit. The broadcasting meansbroadcasts the command signal to the plurality of spread-spectrum units.The receiving means receives the command signal when broadcast from adifferent spread-spectrum unit. The activating means activates theremote subunit upon receiving the command signal.

The initiating means is illustrated in FIG. 3 as a push button switch43. The broadcasting means is illustrated as a transmitter portion ofthe transmitter/receiver 42. The transmitter transmits at frequency f₃.The receiving means is illustrated as the receiver portion oftransmitter/receiver 42. The receiver receives at frequency f₃. Thetransmitter/receiver 42 is coupled to antenna 41 for radiating andreceiving signals. The activating means includes the necessary circuitryfor disconnecting the base subunit and activating the remote subunit ofa particular spread-spectrum unit. The activating means is illustratedas control circuitry 44. The present invention may also be used for datain place of voice signals.

In use, a particular spread-spectrum unit might be operating with itsremote subunit activated. Thus, the remote subunit of that particularspread-spectrum unit receives at the second frequency thebase-spread-spectrum signal, and despreads the base-spread-spectrumsignal as a despread-base-spread-spectrum signal. Thedespread-base-spread-spectrum signal is demodulated. Thus, thatparticular spread-spectrum unit receives all of the base signals via itsremote subunit. While transmitting to the plurality of spread-spectrumunits, that particular spread-spectrum unit converts the voice signal,embodied as the remote-analog signal, to the remote-data signal. Theremote-data signal is spread-spectrum processed and transmitted at thefirst frequency as one of the plurality of spread-spectrum signals.

Upon initiation of the command signal by the user of that particularspread-spectrum unit, by pushing push button 43, that particularspread-spectrum unit switches from operating with the remote subunit tooperating with the base subunit. At the same time, the command signal isradiated to the other spread-spectrum units of the plurality ofspread-spectrum units. Upon receiving the command signal, each of thespread-spectrum units has its remote subunit activated and thereafterworks in a remote subunit mode. The particular spread-spectrum unit hasthen become the base station.

When operating as the base station, the particular spread-spectrum unithas its base subunit activated. Accordingly, the plurality ofspread-spectrum signals transmitted from the plurality ofspread-spectrum units at each unit, is received by the RF/IF amplifierand circuitry 12 via antenna 11. The plurality of spread-spectrumsignals are despread by the plurality of mixers 13, 14, 15, anddemodulated by the demodulator 16 which outputs a demodulated signal.The plurality of demodulated signals from combiner 17A are the voicesfrom the plurality of remote stations. The voices from the plurality ofremote stations are combined with the voice of the base station bycombiner 17B, and converted by analog-to-digital converter 18 to thebase-data signal. The base-data signal is spread-spectrum processed bythe product device 19 and transmitted by transmitter 20 and via antenna21 at the second frequency.

As will be appreciated by those of ordinary skill in the art, an exampleof the spread spectrum unit built as a totally integrated unitreferenced in paragraph [0019] above is a combination of the commandsubunit of FIG. 3 with a base subunit of FIG. 1A or 1B and a remotesubunit of FIG. 2A or 2B where the command subunit antenna 41 serves asboth the transmit and receive antenna for both the base and remotesubunits. Such a combination is an example of a mobile communicationunit that has an antenna and circuitry configured in a first mode as aremote subunit and in a second mode as a base subunit. Such a mobilecommunication unit in the first mode will receive data from a firstcommunication unit such as voices from a base station and output thebase station voices to a user of the mobile communication unit asdescribed in connection with FIGS. 2A and 2B. Such a mobilecommunication unit in the second mode will receive data from acommunication unit such as a voice from at least one remote station andwill transmit the received data to a plurality of mobile communicationunits, i.e. remote subunits, as described in connection with FIGS. 1Aand 1B. The command subunit of such a mobile communication unit permitsit to switch from the first mode to the second mode in response to aninput from a user of the mobile communication unit, such as via switch43. Accordingly, switch 43 permits a user of the mobile communicationunit to switch between the first mode and the second mode in response tothe user switching the switch that then serves as an input to thecommand subunit. It thus follows that, on a condition that the mobilecommunication unit is in the first mode, data is received from a firstcommunication unit and output to the user of the mobile communicationunit. It further follows that, on a condition that the mobilecommunication unit is in the second mode, data is received data from atleast one second communication unit and transmitted data to a pluralityof third mobile communication units, i.e. remote subunits.

What is claimed is:
 1. A control device in a mobile communication unitcomprising: circuitry configured to enable the mobile communication unitto operate in a first mode; wherein in the first mode, the mobilecommunication unit receives first data from a first communication unitand outputs the received data to a user of the mobile communicationunit; the circuitry is further configured to enable the mobilecommunication unit to operate in a second mode; wherein in the secondmode, the mobile communication unit receives second data from a secondcommunication unit and transmits the received second data to at leastone of a plurality of third mobile communication units; and thecircuitry is further configured to switch from the first mode to thesecond mode in response to an input from the user of the mobilecommunication unit.
 2. The control device in the mobile communicationunit of claim 1 wherein the first communication unit and the secondcommunication unit are a same communication unit.
 3. The control devicein the mobile communication unit of claim 1 wherein the received datafrom the first communication unit is in a code division multiple accesssignal.
 4. The control device in the mobile communication unit of claim1 wherein the received data from the first communication unit includesvoice data.
 5. The control device in the mobile communication unit ofclaim 1 wherein the second data is transmitted at a same time to the atleast one of the plurality of third mobile communication units.
 6. Thecontrol device in the mobile communication unit of claim 1 wherein inthe second mode, the antenna and circuitry is configured to broadcastdata to the at least one of the plurality of third stations.
 7. Thecontrol device in the mobile communication unit of claim 9 wherein inthe second mode, the circuitry is configured to further output receiveddata from the at least one second communication unit to the user of themobile communication unit.
 8. A method of enabling a mobilecommunication unit using a control device comprising: configuring themobile communication unit to operate in a first mode; wherein in thefirst mode, the mobile communication unit receives first data from afirst communication unit and outputs the received data to a user of themobile communication unit; configuring the mobile communication unit tooperate in a second mode; wherein in the second mode, the mobilecommunication unit receives second data from a second communication unitand transmits the received second data to at least one of a plurality ofthird mobile communication units; and switching from the first mode tothe second mode in response to an input from the user of the mobilecommunication unit.
 9. The method of claim 8 wherein the firstcommunication unit and the second communication unit are a samecommunication unit.
 10. The method of claim 8 wherein the received datafrom the first communication unit is in a code division multiple accesssignal.
 11. The method of claim 8 wherein the received data from thefirst communication unit includes voice data.
 12. The method of claim 8wherein the second data is transmitted at a same time to the at leastone of the plurality of third mobile communication units.
 13. The methodof claim 8 wherein in the second mode, the antenna and circuitry isconfigured to broadcast data to the at least one of the plurality ofthird stations.
 14. The method of claim 8 wherein in the second mode,the circuitry is configured to further output received data from the atleast one second communication unit to the user of the mobilecommunication unit.